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Mission and responsibilities of the Air Quality Analysis Branch (AQAB)

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recent changes or updates to modeling guidance and policies

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links to other modeling or related sites

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find out who to contact in the Air Quality Analysis Branch (AQAB)

This page was developed to speed the transfer of modeling guidance updates to the North Carolina modeling community.

• Updates to AERMOD and AERMET
  An updated version of AERMOD (dated 12345) has now been posted to the SCRAM website and replaced the previous version of AERMOD (dated 12060). A summary of the changes incorporated into version 12345 of AERMOD can be found in Model Change Bulletin #8 (MCB#8). An update to the AERMOD User's Guide Addendum along with a new compliment of Test Cases have also be post on SCRAM. The respective link to the updated version of AERMOD is http://www.epa.gov/ttn/scram/dispersion_prefrec.htm#aermod

   

  Additionally, an updated version of AERMET (dated 12345) has been posted to the SCRAM website and replaced the previous version of AERMET (dated 11059). A summary of the changes incorporated into version 12345 of AERMET can be found in Model Change Bulletin #3 (MCB#3). An update to the AERMET User's Guide Addendum along with a new compliment of Test Cases have also be post on SCRAM. The respective link to the updated version of AERMET is http://www.epa.gov/ttn/scram/metobsdata_procaccprogs.htm#aermet

• NCDAQ Screen Modeling Policy
  Effective immediately, the preferred screening model for NCDAQ is AERSCREEN. As of January 2, 2013, SCREEN3 will not be accepted. In the interim time, SCREEN3 may be accepted if specifically approved by NCDAQ/AQAB. All NCDAQ/AQAB guidance documents will be updated as soon as possible to reflect this status.

• Updated PSD Modeling Guidance
  A new version of the NCDAQ PSD Modeling Guidance, which makes some small corrections, has been loaded on this website. To view the document click here.

• Updated Protocol Checklist
  The North Carolina Modeling Protocol Checklist has been revised and now includes a requirement to identify the facility ID, where applicable, (previous update) and to identify the coordinate system used in the refined modeling analysis. Please be advised that if the new checklist is not submitted, you will receive a request to do so before the modeling is reviewed.

• Updated Protocol Checklist
  The North Carolina Modeling Protocol Checklist has been revised and now includes a requirement to identify the facility ID, where applicable, (previous update) and to identify the coordinate system used in the refined modeling analysis. Please be advised that if the new checklist is not submitted, you will receive a request to do so before the modeling is reviewed.

• Updated PSD Modeling Guidance
  A new version of the NCDAQ PSD Modeling Guidance has been loaded on this website. To view the document click here.

• New Coastal Area Met Set for AERMOD
  AQAB has created a new processed meteorological dataset for AERMOD use. The surface data are from Beaufort, and the upper air data are from Newport (dates = 2005 to 2009). See our updated guidance (click here) for instruction on where to use this new data.

• Interim PM 2.5 SIL Established
  Until EPA develops and promulgates the 24-hr and annual SILs for PM2.5, NCDAQ has adopted interim PM2.5 SILs of 1.2 ug/m3 (24-hr) and 0.3 ug/m3 (annual). The interim SILs represent the third option currently being proposed by EPA and were derived by adjusting the PM10 SILs as a proportion of the NAAQS ratio of PM2.5 to PM10.

• Interim SO₂ 1-hr SIL Established
  Until EPA develops and promulgates a 1-hr SO2 SIL for the recently promulgated SO2 1-hr NAAQS, NCDAQ has adopted an interim 1-hr SO2 SIL of 10 ug/m3. The 10 ug/m3 SIL was derived using the same procedures developed by the Northeast States for Coordinated Air Use Management (NESCAUM) for the 1-hr NO2 SIL (also adopted by DAQ - see alert for Interim NO2 1-hr SIL) and is based on the ratio of the existing 1-hr CO SIL to the 1-hr CO NAAQS.

• Interim NO₂ 1-hr SIL Established
  Until EPA develops and promulgates a 1-hr NO2 SIL for the recently promulgated NO2 1-hr NAAQS, NCDAQ has adopted an interim 1-hr NO2 SIL of 10 ug/m3. The 10 ug/m3 SIL was developed by the Northeast States for Coordinated Air Use Management (NESCAUM) and is based on the ratio of the existing 1-hr CO SIL to the 1-hr CO NAAQS.

• New PSD AERMOD Meteorology
  Effective immediately, PSD modeling using AERMOD will require use of revised meteorological data sets based on surface roughness associated with the modeled facility location. For details on the modeling approach and new meteorological data click HERE.

• NCDAQ Screening Meteorology in AERMOD is Rescinded
  Effective immediately the option of using the NCDAQ screening meteorology in AERMOD is rescinded. This primarily affects modeling in the Western portion of NC. Our modeling guidance will be updated soon to reflect this policy. To view our updated Western NC modeling guidance, click HERE.

• Updated Toxics Modeling Guidance
  An updated version of the "Guidelines for Evaluating The Air Quality Impacts of Toxic Pollutants in North Carolina" is posted on this website. All previous versions are obsolete. You can review the new guidelines by clicking HERE.

• NCDAQ PSD Modeling Requirements
  Effective immediately, the NCDAQ PSD modeling requirements will include an evaluation and, as applicable, modeling of "primary PM2.5" (filterable and condensable) emissions. Modeling for PM2.5 will be required whenever the PSD PM10 Significant Emission Rates (SERs) are exceeded. Modeling for PM2.5 may also be required, pursuant to 15A NCAC 2D .0501, whenever an increase in PM2.5 emissions is expected even if the PM10 SERs are not exceeded; this requirement will be evaluated on a case-by-case basis and will be discussed during the PSD Pre-application meeting. Click HERE for guidance for conducting PM2.5 modeling.

• AQAB Policy on USGS NED Data
  For AERMOD applications, AQAB prefers use of the USGS elevation data from the National Elevation Database (NED). The old DEMs for NC have a number of documented problems that are corrected in the NED data.

• Update Protocol Checklist and D3 Form
  The AQAB Protocol Checklist and the D3 Form have been updated to require facility IDs and to incorporate new guidance on terrain modeling recommendations. To download click here (Protocol Checklist and D3 Form).

• PSD Guidance Update
  Updates / Corrections to Section 5.

• AERMOD Met Policy Update
  All AERMOD submissions must use the processed meteorology that is currently available on the DAQ/AQAB website. Earlier versions will not be accepted. The AQAB routinely reviews the meteorological data used to ensure the appropriate data has been selected.

• Processed AERMOD met data updated.
  Asheville and Raleigh met data updated.

• Western NC Modeling Guidance Posted
  The NCDAQ/AQAB has posted guidance for modeling in Western North Carolina to provide strategies for the mountainous region. To download, click HERE.

• NC PSD Guidance Updated
  The NCDAQ/AQAB has updated the North Carolina PSD modeling guidance. To download, click HERE.

• Processed AERMOD met data updated.
  Go to our meteorological data page to download the data set you need. Use of these data sets is required in NC, unless AQAB approves otherwise on a case-by-case basis.

• NC PSD Guidance Published
  The NCDAQ/AQAB has developed modeling guidance to assist the PSD permit applicant to identify and comply with the modeling requirements associated with the PSD permitting process. This guidance will be routinely updated to incorporate new or revised PSD modeling requirements/methodologies and as such, we encourage the user to periodically check the AQAB web site for the latest guidance and download, as necessary. We also encourage user feedback for suggested guidance changes or additions. To download, click HERE.

• Update to Toxics Modeling Guidelines
  To download, click HERE.

• Processed AERMOD met data available.
  Go to our meteorological data page to download the data set you need. Use of these data sets are required in NC, unless AQAB approves otherwise on a case-by-case basis.

• Update to Toxics Modeling Guidelines
  To download, click HERE.

• Update to Protocol Checklist
  To download, click HERE.

• New TSP Modeling Policy
  Effectively immediately, TSP (PM 0-100 microns) will be evaluated consistent with that of a NC air toxic. The TSP air quality analysis will use modeled receptors beginning at the facility property line and will exclude background TSP concentrations and offsite source impacts. In addition, modeled receptors along public right-of-ways traversing the facility property will not be required. DAQ will continue to accept the preliminary impact analysis approach to determine if a full impact TSP analysis will be required.

• UPDATE TO QUARRY MODELING GUIDELINES:
  An update to AQAB's Quarry Modeling Guidelines has been made. It is available on our Modeling Page: To download, click HERE.

• MONCURE AREA CRITERIA AND TOXIC POLLUTANT IMPACT STUDY:
  This modeling report details the Division of Air Quality¿s efforts to evaluate SO_2 and formaldehyde impacts in the Moncure, Chatham County area and the permitting actions taken to ensure compliance with all applicable air quality standards. Click HERE for a pdf copy of report.

• QUARRY MODELING UPDATE:
  Effective immediately, TSP background concentrations will no longer be required to be added to the modeled TSP impacts from quarry operations. The quarry impacts will be compared directly to the TSP NCAQS. The AQAB Quarry Modeling Guidance has been updated to reflect this policy.

• TRANSPORTATION FACILITY GUIDLINES:
  An updated version of the Transportation Facility Guidelines has been posted on this website.

• AERMOD IMPLEMENTATION STRATEGY:
  Effective November 9, 2005, AERMOD is the DAQ-preferred model for most refined modeling applications, replacing ISCST3, and will be the primary model used by DAQ to evaluate facility compliance or perform modeling as a part of any DAQ special modeling study.
   
  During the one-year AERMOD implementation period ending November 9, 2006, permit applicants will be encouraged to use AERMOD; however, ISCST3 may be used at the user's discretion. After that date, AERMOD will be required for appropriate regulatory compliance modeling applications. ISCST3 use will be limited and must be pre-approved by DAQ.